Abstract Objective To explore the effect of neonatal maturity and postnatal age on serum potassium concentration ([K +]). Methods Serum [K +] in neonates with gestational ages of 24～28 weeks (group A), 29～32 weeks (group B), 33～36 weeks (group C) and 37～42 weeks (group D) were retrospectively analyzed at 1～72 hours after birth. Results ①There was a linear correlation between serum [K +] and the gestational age, birth weight, and urine output in newborns. ②Serum [K +] of group A and B was higher than that of group C and D during the first 24 hours after birth, decreased during the second 24 hours, and reached that of group C and D during the third 24 hours. Serum [K +] in groups C and D did not change significantly during 72 hours after birth. ③Twenty four of the premature infants in groups A, B and C developed hyperkalemia (≥7.0 mmol/L) during the first 24 hours, with an incidence of 20.0%, 12.5% and 4.0%, respectively. After conventional therapy, serum [K +] in 14(58.3%) decreased to less than 7.0 mmol/L within 72 hours (all infants survived), whereas hyperkalemia persisted in 10 infants (41.7%) remained, and 7 died. There was no hyperkalemia in group D during 72 hours after birth. Conclusions Neonatal maturity and postnatal age affect serum potassium concentration. Higher potassium concentration decreases with the increasing of gestational and postnatal age in very premature infants. Critical hyperkalemia exists in premature infants, and conventional therapy is partially effective for the survival of the infants.
